Cleanup rustc/driver

[ljedrz]

• improve/remove allocations
• simplify profile::trace::cons*
• don't sort base if it only has one element
• use Cow<str> where applicable
• use unwrap_or_else with function calls
• remove an explicit return, add an explicit None
• remove lifetimes from consts
• improve common patterns
• improve macro calls
• whitespace & formatting fixes

[rust-highfive]

r? @estebank

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[ljedrz]

Hmm, I'm not sure if this is spurious or not; I'll verify shortly.

[estebank]

LGTM, couple of nitpicks.

[estebank]

I'm wondering wether the previous version was like that to avoid flushing on every line (I believe that is a behavior difference between write and writeln, although looking around https://llogiq.github.io/2017/06/01/perf-pitfalls.html https://www.reddit.com/r/rust/comments/6hoayo/how_do_i_write_to_stdout_without_line_buffering/ it seems like I might be wrong).

[ljedrz]

Good point; this change is contained in a single commit, so in case of any issues it can be easily reverted. I can also pull it back if you prefer.

[estebank]

unwrap_or_else(PathBuf::new);

[ljedrz]

Or unwrap_or_default that I forgot existed ^^.

[estebank]

I think this should work: .unwrap_or_else(input.filestem);

[ljedrz]

That would be cool, but unfortunately the compiler recognizes this as E0615.

[estebank]

That's annoying but can see how it happens. Thanks for checking.

[estebank]

Given the indentation here, wouldn't the following be better?

	                        let emitter = errors::emitter::EmitterWriter::stderr(
	                            errors::ColorConfig::Auto,
	                            None,
	                            true,
	                            false,
	                        );

[estebank]

When encountering these I usually change them to be

fn foo(
    &self,
    bar,
) -> A {
}

That way we won't have to worry about the function name changing length or adding/removing type args/lifetimes requiring reindenting of the arguments.

[estebank]

[00:21:43] error: unused attribute
[00:21:43]  --> rustc/compiler_builtins_shim/../../libcompiler_builtins/src/lib.rs:5:1
[00:21:43]   |
[00:21:43] 5 | #![crate_type = "rlib"]
[00:21:43]   | ^^^^^^^^^^^^^^^^^^^^^^^
[00:21:43]   |
[00:21:43] note: lint level defined here
[00:21:43]  --> rustc/compiler_builtins_shim/../../libcompiler_builtins/src/lib.rs:1:31
[00:21:43]   |
[00:21:43] 1 | #![cfg_attr(not(stage0), deny(warnings))]
[00:21:43]   |                               ^^^^^^^^
[00:21:43]   = note: #[deny(unused_attributes)] implied by #[deny(warnings)]
[00:21:43] 
[00:21:43] error: crate-level attribute should be in the root module
[00:21:43]  --> rustc/compiler_builtins_shim/../../libcompiler_builtins/src/lib.rs:5:1
[00:21:43]   |
[00:21:43] 5 | #![crate_type = "rlib"]
[00:21:43]   | ^^^^^^^^^^^^^^^^^^^^^^^
[00:21:43] 
[00:21:43] error: aborting due to 2 previous errors
[00:21:43] 
[00:21:43] error: Could not compile `compiler_builtins`.

[ljedrz]

Error fixed, comments addressed.

[estebank]

@bors r+

[bors]

📌 Commit b03a82c has been approved by estebank

[bors]

⌛ Testing commit b03a82c with merge f02768b...

[bors]

☀️ Test successful - status-appveyor, status-travis
Approved by: estebank
Pushing f02768b to master...